Vulcanizable composition comprising halogenated butyl rubber and stannous chloride and method of vulcanizing same



United States Patent VULCANIZABLE COMPOSITION COMPRISING HALOGENATED BUTYL RUBBER AND STANNOUS CHLORIDE AND METHOD OF VULCANIZING SAME Leon-S. Minckler, Jr., Metuchen, Delmer L. Cottle, Highland Park, and Theodore Lemiszka, Rahway, N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware No Drawing. Filed May 16, 1957, Ser. No. 659,469

17 Claims. (Cl. 260-415) This invention relates to rubbery polymeric compositions which are halogenated copolymers of isoolefins and multiolefins and to the preparation and vulcanizationof such compositions and more particularly to improved methods for curing halogenated butyl rubber with minor proportions of stannous chloride.

Copolymers of the above general type, especially where the copolymer contains about 85 to 99.5% (preferably about 95 to 99.5%) of a C to C isoolefin such as Z-methyl-l-butene, 3-methyl-1-butene or isobutylene with about 15 to 0.5% (preferably 5 to 0.5 weight percent) of a multiolefin of about 4 to 14, preferably about 4 to 6 carbon atoms and having a Staudinger molecular Weight of between about 20,000 to 300,000 are commonly referred to in patents and literature as butyl rubber or GR-I rubber (Government Rubber-lsobutylene) and, for example, is referred to as butyl rubber in textbook Synthetic Rubber by G. S. Whitby. The preparation of butyl type rubber is described in US. Patent 2,356,128 to Thomas et a1. as well as in technical literature. In general, the multiolefinic component of the rubber comprises such multiolefins as myrcene, allo-ocymene or dimet-hallyl or preferably a conjugated diolefin such as isoprene, butadiene, dimethyl butadiene, piperylene, etc. The reaction product of isobutylene and isoprene is preferred. Butyl rubber has a mole percent unsaturation of between about 0.5 to 15.0.

.Halogenated butyl-type rubbery copolymers, which are vulcanizable with zinc oxide and covulcanizable with more highly unsaturated rubbers, are produced 'by halogenating the butyl rubber in a manner which does not appreciably degrade the molecular Weight thereof, but halogenated sufliciently to produce a rubbery product which when vulcanized retains its tensile strength upon heat aging. Such halogenated butyl rubbers are readily t covulcanizable with more highly unsaturated rubbers with or without added sulfur to produce rubbery products of excellent heat aging resistance. The halogenated butyl rubbers so formed also do not greatly .diifer in curing rate as compared to natural rubber and synthetic rubbers such as GRS rubber.

It has now been discovered that halogenated butyl vrubber may be cured with stannous chloride to produce vulcanizates having improved tensile strength compared to zinc oxide cured vulcanizates.

In practicing the present invention, 100 parts by Weight of halogenated butyl rubber are compounded with about 2 to 30 advantageously about 3 to 20 parts by Weight of stannous chloride and preferably also with about 20 to 100 parts by weight of a filler such as clays or carbon blacks, with the optional addition of such conventional compounding agents as antioxidants such as phenyl betanaphthylamine, sulfur, sulfur-containing accelerators, quinoid compounds, antitack agents such as stearic acid or zinc stearate, resins, plasticizers, etc. The resulting compounded stock is then cured by heating the same for ice about 0.5 minute to 5 hours, preferably for about 2 min utes to 2 hours at a temperature level of between about to 400 R and preferably at about 200 to 300' E, to produce a vulcanizate having excellent tensile strength.

In producing halogenated butyl rubber .to be vu'lcanized in accordance with the present invention, unmodified, unvulcanized butyl rubber is carefully halo genated so .as to contain about at least 0.5 weight percent (preferably at least about 1.0 weight percent) combined halogen but not more than about X weight percent com; bined chlorine or 3X weight percent combined bromine wherein:

aten d D c 0, 9 0

and

L :mole percent of the multiolefin in the polymer. M =molecular weight of the isoolefin. M =molecular weight of the multiolefin. M =atomio weight of chlorine or bromine.

Restated, there should be at least about 0.5 weight percent of combined halogen in the polymer but not more than about one atom of chlorine or three atoms of bromine combined in the polymer per molecule of multiolefin present therein; i.e. not more than about one atom of .COmbined chlorine or three atoms of combined bromine per double bond in the polymer.

.Suitable halogenating agents which may "be employed are gaseous chlorine, liquid bromine, alkali metal hypochlorites, sodium hypobromite, C to C tertiary alkyl'hypochlorites or hypobromites, sulfur chlorides or bromides (Particularly oxygenated sulfur chlorides or bromides), pyridinum chloride perchloride, N-bromo-succinimide, iodine monochloride, alphachloroacetanilide, tri-bromophenol :bromide, N-chloroacetamide, N,N-dimethyl-5,5 dichloro .or dibromo 'hydantoin, and other common halogenating agents.

The halogenation is generally conducted at above 0 to about +200 C., advantageously at about 10- to 65 C., preferably at about 20 to 50 C. (room temperature being satisfactory), depending upon the particular halogenation agent, for about one minute to several hours. An advantageous pressure range is from about 0.5 to 400 p.s.i.a.; atmospheric pressure being satisfactory. The halogenation conditions are regulated to halogenate the rubbery copolymer to the extent above-mentioned.

The halogenation may be accomplished in various ways. One process comprises preparing a solution of the copolymer as above, in a .suitable inert liquid organic solvent such as a C to C or preferably a C to Q inert hydrocarbon or halogenated derivatives of saturated hydrocarbons, examples of which are hexane, heptane, naphtha, mineral spirits, cyclohexane, alkyl substituted cycloparafiins, benzene, .chlorobenzene, chloroform, trichloroethane, carbon tetrachloride, mixtures thereof, etc., and adding thereto gaseous chlorine, liquid bromine, or t e halqgena ing a ent, which may p i y be in solution, such as dissolved in any inert hydrocarbon, an alkyl chloride, carbon tetrachloride, etc.

The concentration of the butyl rubber in the solvent will depend upon the type of reactor, molecular Weight of the butyl rubber, etc. -In general, the concentration of a butyl rubber having a viscosity average molecular weight of about 200,000 to about 1,500,000, it the solvent is a substantially inert hydrocarbon, will be between 1 and 30% "by'weight, preferably about 5 to 20%. If chlorine gas is employed to chlorinate such a rubbery solution, 'it may also be diluted with up to about 50 times its volume, preferably about 0.1 to 5.0 times its volume 3 of an inert gas such as nitrogen, methane, ethane, carbon dioxide, etc.

The resulting halogenated butyl rubber polymer may be recovered in various manners. The halogenated polymer may be precipitated with acetone or any other known non-solvent for the halogenated butyl rubber and dried under about 1 to 760 millimeters or higher of mercury pressure absolute at about to 180 C., preferably at about 50 to 150 C. (e.g. 70 C.). Other methods of recovering the halogenated butyl rubber polymer from the hydrocarbon solution of the same are by conventional spray or drum drying techniques. Alternatively the halogenated butyl rubber-containing solution may be injected into a vessel containing agitated water heated to a temperature sufiicient to flash off the hydrocarbon solvent and form an aqueous slurry of the halogenated butyl rubber. The halogenated butyl rubber may then be separated from this slurry by filtration, dried and recovered as a crumb or as a dense sheet or slab by conventional milling and/or extruding procedures. The halogenated copolymer formed advantageously has a viscosity average molecular weight between about 200,000 and 2,500,000 and a mole percent unsaturation of between about 0.5 to 15.0, preferably about 0.6 to 5.0.

In order to more fully illustrate the present invention, the following experimental data are given.

CHLORINATED BUTYL RUBBER A A copolymer of about 97% isobutylene and 3% isoprene having a viscosity average molecular weight of 320,000 was dissolved in hexane to form a solution. To this polymer solution, a 20 weight percent (based on the polymer) of liquid sulfuryl chloride as the chlorinating agent was added and reacted for 30 minutes with the polymer at room temperature. The resulting chlorinated copolymer was precipitated with acetone, collected and redissolved in hexane three times and ultimately dried and analyzed and found to have a viscosity average molecular weight of 320,000 and to contain 1.4% chlorine based on the polymer. The physical characteristics of both zinc oxide and diamine-cured vulcanizates, containing this chlorinated interpolymer, were excellent.

CHLORINATED RUBBERS B TO L Other examples of halogenated isoolefin-multiolefin copolymers which can be used are tabulated hereinafter, the amount of isoolefin and multiolefin in copolymer, halogenation agent, and amount of halogen combined in the copolymer being as follows:

Gaseous chlorine was continuously added to the butyl rubber solution over a period of one-half hour ata temperature level of 30 C. and under atmospheric pressure. The chlorine was added to the reactor through the conduit via the sparger ring. The chlorination was then terminated and the solution containing the chlorinated butyl rubber formed was agitated for an additional 20 minutes. The resulting solution of chlorinated butyl rubber was then water washed three times to remove dissolved hydrogen chloride.

The absolute amount of butyl rubber, benzene solvent and gaseous chlorine added, as well as the calculated percent of added chlorine based on polymer and resulting percent of chlorine combined in the polymer were as follows:

The resulting water-washed solution containing the stabilized, chlorinated butyl rubber M was then recovered by injecting the solution into an agitated aqueous slurry containing zinc stearate and a small amount of the non-ionic wetting agent of the aliphatic polyoxyethylene ether type such as Tergitol NPX (e.g. Sterox AI) in an amount of 0.7 pound of the zinc stearate per 100- pounds of chlorinated butyl rubber as a dispersing aid. The agitated solution was maintained at a temperature between about 190 and 210 F. (e.g., 200 F.) whereby to flash off the benzene solvent and form an aqueous slurry of the chlorinated butyl rubber in water. This slurry was then filtered and the chlorinated butyl rubber, which was in the form of a wet crumb, was placed in a Proctor and Schwartz tray drier maintained at 180 F. (i.e. 82 C.) and dried for 12 hours. The crumb depth on the tray was about /2 inch. The crumb was then completely dried and compacted by milling for 15 minutes on a conventional rubber mill having a. roll temperature of 260 F. (i.e.,127 C.).

Example I 100 parts by weight of chlorinated butyl rubber M were compounded on a cold rubber mill (e.g. 20 C.)

with parts by weight of MPC carbon black, 1 part by weight of zinc stearate, 0.2 part by weight of phenyl- Halogenated (Percent) rubber Isoolefin (percent) 1 Multioletin (percent) 1 Halogenation Agent Halogen in the rubber 1 Isoprene (2) S0 0], 1.2 chlorine.

lsoprene (5.0) Clz in 00h... 2.5 chlorine Cyelopcntadiene C]; in 01 2.0 chlorine Zanethyl-butene-l (95) Isoprene (5)..- Cl; in HeXaue 1.5 chlor ne 3-methyl-butene-1 (96) Butadiene (4) C1 in Hexane 1.9 chlor ne.

l-vinyl cyclohexe C12 in COl 0.8 chlor ne But-adiene (8) gaseous chlorin 2.8 chlorine Isoprenc (15)- do 6.6 chlorine. Isobutylene (98) Isoprene (2) N ,N diehloro 5,5 di- 1.1 chlorine.

methyl hydantoin.

L do -do liquid bromine 2.3 bromine.

1 N own-(Percent) in all instances is percent by weight.

CHLORINATED BUTYL RUBBER M" beta-naphthylamine and 5.0 parts by weight of stannous chloride (SnCl -2H O). Two samples of the resulting compounded stock were taken, one being vulcanized at 260 F. for 5 minutes, the other being vulcanized at 260 F. for 15 minutes. For comparison purposes two controls containing no added stannous chloride were heated under the same conditions with no resulting cure.

' :15 Upon increasing both the temperature and time a partial cure of an additional control sample was obtained. The results were as follows:

The above data show that, under relatively mild vulcanizing conditions, chlorinated butyl rubber cures in the presence of added stannous chloride into good quality vulcanizates but that omitting the stannous chloride results in either no cure or a poorer quality vulcanizate.

Example II 100 parts by weight of a brominated butyl rubber having a Mooney viscosity (212 F. for 8 minutes) of 71, a mole percent unsaturation of 1.8 and a bromine content of 2.4% were compounded with the various amounts of stannous chloride, carbon black, zinc stearate and phenyl betanaphthylamine given in Example I. Vu1- canizates cured for 5 to 30 minutes at 200 F. to 250 F. were compared to control vulcanizates containing zinc oxide in place of stannous chloride with the following results:

Cure conditions Physical Properties Cure System Time, Temp, Tensile, Elonga- Mins. F. Modulus, p.s.i. tion p.s.i. percent stannous chloride-.. 200 320 1, 240 680 zinc oxide 5 200 stannous chloride"- 15 200 380 1, 320 595 zinc oxide 15 200 stannous chloride- 30 200 410 1, 385 600 5 225 400 1, 450 640 5 5 stannous chloride-.. 15 225 405 1, 390 680 zinc oxide 15 225 210 310 805 stannous chloride 80 225 340 1, 280 625 zinc oxide- 30 225 485 970 555 Stamens chlon 5 250 430 1, 415 670 zinc oxi 5 250 210 345 705 The above data show that, under relatively mild vulcanizing conditions, brominated butyl rubber cures in the presence of added stannous chloride into good quality vulcanizates but that replacing the stannous chloride with zinc oxide results in either no cure or a poorer quality vulcanizate.

Resort may be had to modifications and variations of the disclosed embodiments without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

l. A vulcanizable composition comprising a major proportion of a rubbery copolymer of about 85 to 99.5 weight percent of a C to C isoolefin and about 15 to 0.5 weight percent of a C to C multiolefin said copolymer being modified with a halogen selected from the group consisting of bromine and chlorine and a minor proportion of stannous chloride, said stannous chloride being the sole vulcanizing agent.

2. A composition according to claim 1 in which the halogenated copolymer contains at least 0.5 weight percent chlorine but not more than about one atom of chlorine per double bond in the copolymer.

3. A composition according to claim 1 in which the halogenated copolymer contains at least about 0.5 weight percent bromine but not more than about three combined atoms of bromine per double bond in thecopolymer.

4. A composition according to claim 1 in which the stannous chloride is present in an amount of between about 2.0 and 30 weight percent based on halogenated copolymer.

5. A composition according to claim 1 containing about 20 to parts by weight per 100 parts by weight of copolymer of a carbon black.

6. A composition according to claim 1 in which the halogenated copolymer is selected from the group consisting of chlorinated isoolefin-multiolefin butyl rubber copolymers and brominated isoolefin-multiolefin butyl rubber copolymer.

7. A composition according to claim 1 which has been vulcanized by heating the same for between about 0.5 minute and 5 hours at a temperature level of between about 100 and 400 F. to produce a vulcanizate having a high tensile strength.

8. A vulcanizable composition comprising a rubbery polymer having a viscosity average molecular weight of at least about 200,000, containing in its structure a major proportion of hydrocarbon units derived by the polymerization of isoolefins containing about 4 to 7 carbon atoms and a minor proportion of hydrocarbon units in which a pair of carbon atoms is linked by an olefinic double bond that the mole percent unsaturation is between about 0.5 to 15; said polymer containing at least about 0.5 weight percent halogen selected from the group consisting of bromine and chlorine but not more than about one combined atom of halogen per double bond in the polymer; said polymer being in composition with a vulcanizing amount of stannous chloride, said stannous chloride being the sole vulcanizing agent.

9. A composition according to claim 8 in which the polymer contains chlorine.

10. A composition according to claim 8 in which the polymer contains bromine.

11. A composition according to claim 8 in which the stannous chloride is present in an amount of between about 2 and 20 weight percent based on the halogen-containing polymer.

12. A composition according to claim 8 in which the polymer is also in composition with about 20 to 100 parts by weight of a filler per 100 parts by weight of polymer.

13. A composition according to claim 12 in which the filler is a carbon black.

14. A composition according to claim 12 which has been vulcanized for between about 2 minutes and 2 hours at a temperature level of between about 200 and 300 F to produce a vulcanizate having a high tensile strength.

15. A process which comprises vulcanizing an isoolefinrnultiolefin butyl rubber copolymer, which has been modified with a halogen selected from the group consisting of bromine and chlorine, in the presence of about 2.0 to 30.0 weight percent of stannous chloride as the sole vulcanizing agent at a temperature level of between about 100 and 400 F. until the resulting vulcanizate exhibits a tensile strength of at least about 1,000 p.s.i.

16. A process according to claim 15 in which the halogenated butyl rubber contains chlorine.

17. A process according to claim 15 in which the halogenated butyl rubber contains bromine.

References Cited in the file of this patent UNITED STATES PATENTS 2,631,984 Crawford et al. Mar. 17, 1953 2,726,224 Peterson et al. Dec. 6, 1955 2,732,354 Morrissey et al. Jan. 24, 1956 2,825,720 Tawney Mar. 4, 1958 2,829,123 Tawney Apr. 1, 1958 2,829,132 Tawney et al. Apr. 1, 1958 

1. A VULCANIZABLE COMPOSITION COMPRISING A MAJOR PROPORTION OF A RUBBERY COPOLYMER OF ABOUT 15 TO WEIGHT PERCENT OF A C4 TO C7 ISOOLEFIN AND ABOUT 15 TO 0.5 WEIGHT PERCENT OF A C4 TO C14 MULTIOLEFIN SAID COPOLYMER BEING MODIFIED WITH A HALOGEN SELECTED FROM THE GROUP CONSISTING OF BROMINE AND CHLORINE AND A MINOR PROPORTION OF STANNOUS CHLORIDE, SAID STANNOUS CHALORIDE BEING THE SOLE VULCANIZING AGENT.
 5. A COMPOSITION ACCORDING TO CLAIM 1 CONTAINING ABOUT 20 TO 100 PARTS BY WEIGHT PER 100 PARTS BY WEIGHT OF COPOLYMER OF A CARBON BLACK. 